In such a system the subscriber stations will be movable relatively to their relay stations within a range whose radius is determined by the power of the transmitters at each end of the respective links. In order to insure the necessary privacy, each subscriber station conventionally operates on a radio frequency individually assigned thereto. In practice, an operating range with a radius of about 50 meters will allow telephone calls to be received and transmitted anywhere in a subscriber's house. With only a limited number of radio frequencies available, the same frequency will have to be allocated to stations spaced sufficiently far apart to prevent possible cross-talk or listening-in; in rural areas, for example, 40 communication channels may suffice to cover a region of about 3 km in radius. In multidwelling urban housing, however, such a channel allocation would be inadequate.